<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    data_list = [11, 22, 33];
    for (var i = 0; i++; i < data.length) {
        //闭包
        function xx(data) {
            $.ajax({
                url: '...',
                data: {value: data_list[i]},
                success: function (res) {
                    console.log(data)
                }
            })
        }

        xx(i)
    }

    for(var i = 0; i++; i < data.length){
        (function (data){
            $.ajax({
                url: '...',
                data: {value: data_list[i]},
                success: function (res) {
                    console.log(data)
                }
            })
        })(i)
    }
    console.log(i)
</script>
</body>
</html>